The present invention relates to a method and an apparatus for controlling a vehicle cruise, and more particularly to a method and apparatus for controlling an actual vehicle speed, which is a running speed of a vehicle, to a set speed desired by a driver to hold the vehicle at the fixed vehicle speed.
A known vehicle cruise control apparatus of the type mentioned above involves calculating a target acceleration or deceleration from a deviation of an actual vehicle speed from a set speed instructed by a driver, and controlling a throttle valve based on the target acceleration or deceleration to accomplish vehicle cruise. Another known vehicle cruise control apparatus involves calculating a look-ahead vehicle speed, which anticipates an actual vehicle speed, based on the actual vehicle speed and an actual acceleration, calculating a target acceleration or deceleration based on a deviation of the look-ahead vehicle speed from a set speed instructed by a driver and a look-ahead acceleration, and controlling a throttle actuator based on the target acceleration or deceleration to accomplish vehicle cruise.
JP-A-9-86224 and JP-A-2000-108716 disclose prior art techniques related to vehicle cruise control apparatuses of the type mentioned above.
However, since the prior art control apparatuses mentioned above calculate the target acceleration or deceleration from the vehicle speed deviation (deviation of the actual vehicle speed from the set speed) for controlling the vehicle to run at a constant speed, the driver's will cannot be always reflected to the control. Assume, for example, that the driver inputs a set speed, which can cause overshooting, in order to eventually increase a vehicle speed from Vn0 to Vng, as shown in FIG. 8.
In this event, as the vehicle speed deviation of the actual vehicle speed from the set speed gradually increases from timing t1 in FIG. 8, causing a target acceleration to correspondingly increase to a maximum acceleration at timing t4 in FIG. 8, in which case, however, the acceleration from timing t1 to timing t4 in FIG. 8 is felt rather slow, causing the driver to feel awkward. In addition, the acceleration is gradually reduced between timings t6 and t7 in FIG. 8, in which the vehicle speed deviation begins to decrease, after the vehicle has accelerated to the maximum acceleration (between timings t4 and t6 in FIG. 8), whereas the vehicle speed deviation still has a positive value, and a relatively large acceleration is maintained until timing t7 in FIG. 8 at which the set speed intersects the actual vehicle speed, i.e., at which the vehicle speed deviation decreases to zero (Vs−Vn=0 km/h), so that a subsequent deceleration is delayed (t7−t10). Consequently, the actual vehicle speed is delayed with respect to the set speed, causing the vehicle to feel awkward.